ABSTRACT (PROJECT 4) Evidence from this program project (PPG) demonstrated that defects in genome maintenance cause premature aging in mice. The contribution of genome maintenance to human longevity, however, remains to be established. The main objective of Project 4 (Previous Project 5) has been to translate the PPG's breakthrough discoveries into the human situation by testing the hypothesis that polymorphic variation at loci involved in genome maintenance relates to longevity and healthy aging phenotypes in humans. Research in Project 4 has led to the discovery of genetic and epigenetic signatures associated with human longevity: (1) enrichment of rare variants predicted to change the function and/or expression of proteins involved in signaling and repair of DNA double strand breaks (DSBs) in centenarians as compared to controls; and (2) upregulated microRNAs (miRNAs) in both immortalized B-cells and plasma of centenarians as compared to controls. Interestingly, some of these miRNAs were found, by Project 1, to induce cell preservation responses and cell death repression in the presence of unrepaired DNA damage. We hypothesize that a cluster of protective (epi)genotypes in the genome maintenance gene regulatory network is necessary to achieve exceptional longevity in humans. To confirm and extend our observations that support this hypothesis, we propose a systematic multidisciplinary approach to validate the longevity-associated (epi)genotype signatures and investigate the underlying molecular mechanisms to ascertain the functional relevance of observed positive associations by testing various parameters of cellular fitness in short-term cell culture studies in collaboration with all other Projects. Functionally relevant gene variants and miRNAs will then be further studied for their in vivo effect during aging by modeling them in the mouse in collaboration with Core B. The information generated in Project 4 will provide a mechanistic understanding of the causal relationships between genotypes, miRNA expression, and the associated phenotypes, potentially leading to interventions that promote survival and health in people without genetic predisposition to exceptional longevity.